Micro-Electro-Mechanical Systems, or MEMS devices can be defined as micro-scale mechanical and electro-mechanical systems where at least some elements have some sort of mechanical functionality. Since MEMS devices can be created with the same tools used to create integrated circuits, micromachines and microelectronic elements can be fabricated on a piece of silicon to enable various types of devices.
The dimensions of microelectromechanical devices are very small, the components typically range in size from tens of micrometers to some millimeters. This means that mechanical deformations, displacements or deflections detected in the microelectromechanical devices are also small, and thereby vulnerable to external disturbances. This imposes many challenges to the design. With microelectromechanical devices, a die that comprises a microelectromechanical element and at least one more die that comprises electronics associated to the microelectromechanical element are typically encapsulated into a package.
However, the height of the package is becoming a bottleneck for microelectromechanical devices, which are typically stacked with an integrated circuit die on a carrier and then over-molded. In this traditional way the height has in best examples been in the order of 0.8 mm. However, decreasing it further does not seem to be possible due to problems in handling of very thin dies, wire bonding loop height, thickness of the adhesive layers and thickness of the carrier.